Anticorrosive aluminium light alloy



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ANTICORROSIVE ALUMINIUM LIGHT ALLOY Filed Jan. l2, 1951 2 SheetS-Sheet 22 5 4 6' '7 a `9 lo TDv FFl CEl ITYRG IYT 0F SUGAMO-MACEI,KYITATOSHIM'A-GUN, TGKYO, JAPAN, ASSIGNOR T0 MITSUBSHI ZOSEN KAB'D'SHEKIKAISHA, OF TOKYO, JAPAN' ANTICORROSVTE ALUMINIUM LIGHT ALLOY Applicationler January 12, 1931. Serial No. 508,217.

The present invention relates to an alloy the principal constituent ofwhich is aluminum.

According to the invention the alloy contains chormium, magnesium, andiron in the proportions of 0.5 to 5.0 per cent., 0.5 to 7.0

per cent., and 0.3 to 4.0 per cent. respectively, and the remainder ofaluminum, the latter being allowed to contain small quantities ofimpurities. In fact, the limitation of the quantities of theseconstituents of the alloy as mentioned is .the essential feature lof theinvention.

The invention has for its main object to improve known light alloys andthereby to completely eliminate their deficiencies or drawbacks of beingcorrosive against sea water and poor in mechanical strength, and thus toobtain an alloy which, besides being very anticorrosive to sea water,has more excellent mechanical properties than those in the known alloysof this kind.

The new alloy of the invention is also easily cast accompanying almostno casting hives nor cracks. It can be easily rolled for making plates,wires, pipes and the like, and also be safely forged to manufacturevarious kinds.

of articles of complicated nature. It may be said to be at the stage ofalmost perfection in the anticorrosive property to sea water.

The accompanying drawings are for helping the understanding of theinvention, in which Figs. 1, 2 and 3 are curve diagrams illustrating theeect of respectively chro-` mium, magnesium and iron upon strength orelongation of aluminum; Fig. 4 shows the similar curve diagram when bothmagnesium and iron are alloyed with aluminum.

' The new alloy may be manufactured as follows iChromium and iron arenot used `:in form of pure metal as their melting points are too high,and are preferably taken in the form of anA aluminum primary alloypreparatoryprepared and containing about 25 per cent. of combinedquantity of chromium and iron. In the first step, aluminiun is melted,and then the said primary alloy is added thereto, and after thoroughlyfused, the crucible containing the fused mixture is taken out of thehearth. To this mixture is added magnesium while vigorously stirring byiron bar, and after removing sediments there is obtained a final productwhich can be easily cast in a known manner.

The addition of chromium of 0.5 per cent. or above materially increasesthe resistance to the corrosive action of sea water. And it is obviousfrom Fig. l that the addition of chromium increases at the'same time themechanical strength. Itis, however, seen from the saine .figure that theaddition of chromium in excess affects the reduction of strength, andparticularly of elongation. From these reasons, according to theinvention, the limit of chromium is taken from 0.5 l

to 5.0 per cent. n The purpose of alloying magnesium is similar to thatof chromium. Fig. 2 shows the efi'c'ct of this metal when alloyed withaluminum and by the same reasons, the limits of the quantity ofmagnesium is taken in the range of 0.5 to 7.0 per cent.

It is further found that chromium is more -advantageously used incombination with magnesium, although both are used for the same purpose.That is to say, the sol"e use of chromium over 2.5 per cent. results inrendering the fracture surface of an alloy very bad, while the use ofchromium in combination with magnesium, even at the proportions. of 2.0per cent. of the former, and of 1.5 per cent. of the latter, amountingin all to `3.5 per cent., does not result in making the said surfacebad. Besides, the two metals, being used in more increased quantity thanin the case of either of them being used alone, tends to increase thestrength of alloy. It is for this reason thatl chromium or magnesium isnot used alone, but used in combination in order not only to make morecomplete the anticorrosive property of the alloy, but also to materiallyimprove the mechanical properties of the same. l

According to the invention, the addition of iron increases' the strengthof aluminum, as seen from Fig. 3. But the amount of addition of ironmust be. belowA 40 per cent., because, if this extent is passed, it isfound the fracture surface of the alloy becomes bad. l Hence the limitsof iron istaken from 0.3

to4 4.0 percent. Here-it is found that the addition of iron to suchextent never affects the anticorrosive property ofthe alloy. It is alsofound that, as seen from Fig.- 4, iron is more effective in increasingmechanical strength when it is'used together with magnesium thanif usedalone. In other words, the addition of iron up to 5 per cent. to thealloycontaining 1.0 per cent. of magnesium increases the strengththereof, while, when this limit is passed, the stren th is reduced.Moreover, although the addltion of 5 per' cent. of iron, becomes thecause of making -the fracture surface bad, this defect is eliminated inthe presenceof 1.0 per cent. of magnesium. Therefore the combined use ofmagnesium and iron to the extents serves not only to increase mechanicalstrength, but

also to improve the nature of fracture sur' face. A A

The alloy of the invention has a specific gravity of about 2.73, whichindicates its being very light. l

The uses of the alloy are found in various i directions, sayfor themanufacture of ipes,

` plates, wlres,

ars, and so forth, and ue to its great strength itmay mostadvantageously be used for constructing aeroplanes and automobiles andalso their fittings. The alloy finds its uses almost in all directionsof castings. It may be said, however, that the alloy may, above all,most convemently be used for material in regard to ships and hydroplanesin viewl of its unequalized anticorrosive property.

Claim: I s

An alloy containing 0.5 to 5.0 per cent. of chromium, 0.5 to 7.0 percent. of magnesium,

0.3 to 4.0 per cent of iron and the remainder of aluminum with itsimpurities.

In testimony whereof VI affix my signature.

' ITYRO IYTAKA. y

